Influence of surface modification on the dispersion of nanoscale α‐Al 2 O 3 particles in a thermoplastic polyurethane matrix

In this study, two types of nanoscale α‐Al 2 O 3 particles were used for preparation of α‐Al 2 O 3 /thermoplastic polyurethane (TPU) composites. These α‐Al 2 O 3 particles were either coated or uncoated with stearic acid. For the uncoated α‐Al 2 O 3 /TPU composite, the results of field‐emission scanning electron microscopy (FE‐SEM) and energy dispersive X‐ray spectrometry indicate that uncoated α‐Al 2 O 3 particles are significantly aggregated together. This aggregation is due to the poor compatibility between the inorganic filler (α‐Al 2 O 3 ) and the organic matrix (TPU). The size of clusters is in the range from 5 to 20 μm. For the coated α‐Al 2 O 3 /TPU composite, FE‐SEM results indicate that most coated α‐Al 2 O 3 particles are well dispersed in the TPU matrix. This phenomenon results from the effect of surface modifier (i.e., stearic acid) on α‐Al 2 O 3 particles. Stearic acid can act as a compatibilizer to bridge the boundary between the TPU matrix and the α‐Al 2 O 3 particle. Stearic acid is not only a suitable surface modifier for the nanoscale α‐Al 2 O 3 particle, but also a good dispersant for the dispersion of nanoscale α‐Al 2 O 3 particles in the TPU matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008